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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 210927A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 654396242)
  2. GRB 210925B: AstroSat CZTI detection
  3. IceCube-210922A: SMA observation for the JCMT candidate
  4. IPN triangulation of GRB 210925B
  5. GRB 210926A: AstroSat CZTI detection
  6. GRB 210919A: iTelescope T-11 upper limits
  7. IceCube-210926A: No neutrino counterpart candidates in ANTARES search
  8. GRB 210926A: GECAM detection
  9. GRB 210927A: Fermi GBM Final Real-time Localization
  10. GRB 210919A OSN 1.5m Source Confirmation
  11. GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
  12. IceCube-210922A: JCMT/SCUBA2 observations
  13. GRB 210925A: GECAM detection
  14. GRB 210925A: Fermi GBM Final Real-time Localization
  15. GRB 210919A: Chandra rapid ToO upper limit
  16. GRB 210924A: Fermi GBM Final Real-time Localization
  17. IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations
  18. IceCube-210922A: No significant detection in HAWC
  19. IceCube-210922A: No neutrino counterpart candidates in ANTARES search
  20. GRB 210923B: GECAM detection
  21. Retraction of Fermi GBM GRB 210923A: the trigger is not a GRB
  22. IceCube-210922A: Upper limits from a search for additional neutrino events in IceCube
  23. IceCube-210922A: Upper limits from Fermi-GBM Observations
  24. IceCube-210922A: No Candidate Counterparts from the Zwicky Transient Facility
  25. GECAM observations of a series of bursts from SGR J1935+2154 (2021-09-15T14 to 2021-09-23T14)
  26. GRB 210919A: DECam Upper Limits
  27. Fermi-LAT Gamma-ray Observations of IceCube-210922A
  28. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 September 22
  29. GRB 210923A: Fermi GBM Final Real-time Localization
  30. IceCube Alert 210922.76: Global MASTER-Net observations report
  31. GRB 210919A: Swift-BAT refined analysis
  32. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  33. GRB 210912A: LBT optical observations
  34. GRB 210919A: Lowell Discovery Telescope upper limits (correction to GCN 30859)
  35. GRB 210919a: Lowell Discovery Telescope upper limits
  36. GRB210919A: Keck NIRC2 Kp band upper limits
  37. GRB 210919A: Swift/UVOT Upper Limits
  38. GRB 210919A: LOAO and LSGT optical upper limits
  39. GRB 210919A: MITSuME Akeno optical upper limits
  40. GRB 210919A: Swift-XRT refined Analysis
  41. GRB 210919B: Fermi GBM Final Real-time Localization
  42. GRB 210919A: NOT upper limits
  43. GRB 210919A: AbAO optical upper limit
  44. GRB 210919A: Enhanced Swift-XRT position
  45. GRB 210919A: LCO Optical Upper Limit
  46. GRB 210919A: BOOTES-2/TELMA optical upper limit
  47. Swift GRB 210919A: Global MASTER-Net observations report
  48. GRB 210919A: Swift detection of a short burst
  49. Swift trigger 1073821: detection of IGR J16418-4532
  50. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  51. GRB 210917A: Fermi GBM Final Real-time Localization
  52. GRB 210812A is not a compelling example of a lensed GRB
  53. GECAM observations of bursts from SGR J1935+2154 (2021-09-13T01 to 2021-09-15T14)
  54. GRB 210909A: Detection by GRBAlpha
  55. GRB 210912A: Swift-BAT refined analysis
  56. Konus-Wind observation of the recent SGR 1935+2154 activity
  57. GRB 210912A: Tautenburg observations
  58. GECAM observations of bursts from SGR J1935+2154 (2021-09-12T05 to 2021-09-13T01)
  59. AGILE observations of two bright bursts from SGR 1935+2154
  60. GRB 210912A: CAHA 2.2m Detection
  61. GRB 210912A: Swift-XRT refined Analysis
  62. GRB 210912A: Swift/UVOT Detection
  63. Fermi GBM observation of another bright burst in the direction of SGR 1935+2154
  64. GRB 210912A: Enhanced Swift-XRT position
  65. GRB 210912A: Host-galaxy candidate in PanSTARRS
  66. Fermi trigger No 653151835: Global MASTER-Net observations report
  67. Fermi trigger No 653124492: Global MASTER-Net observations report
  68. Fermi trigger No 653122278: Global MASTER-Net observations report
  69. GRB 210912A: Mondy optical afterglow confirmation
  70. Swift GRB 210912A: Global MASTER-Net observations report
  71. GRB 210912A: BOOTES-5/JGT optical afterglow candidate
  72. GECAM observations of bursts from SGR J1935+2154 (2021-09-11T07 to 2021-09-12T08)
  73. GRB 210912B: Fermi GBM Final Real-time Localization
  74. GRB 210912A: Swift detection of a burst
  75. Fermi trigger No 653093506: Global MASTER-Net observations report
  76. Fermi trigger No 653066776: Global MASTER-Net observations report
  77. Fermi trigger No 653084584: Global MASTER-Net observations report
  78. Fermi trigger No 653083551: Global MASTER-Net observations report
  79. Fermi trigger No 653079281: Global MASTER-Net observations report
  80. Fermi trigger No 653066130: Global MASTER-Net observations report
  81. Fermi trigger No 653072474: Global MASTER-Net observations report
  82. Fermi trigger No 653071808: Global MASTER-Net observations report
  83. Fermi trigger No 653054042: Global MASTER-Net observations report
  84. Fermi trigger No 653049776: Global MASTER-Net observations report
  85. Fermi trigger No 653022153: Global MASTER-Net observations report
  86. Fermi trigger No 653031163: Global MASTER-Net observations report
  87. Swift GRB210910.42: Global MASTER-Net observations report
  88. Fermi GBM observation of a bright flare in the direction of SGR 1935+2154
  89. Fermi trigger No 653010039: Global MASTER-Net observations report
  90. Konus-Wind detection of the second intermediate flare from SGR 1935+2154
  91. IPN triangulation of a bright burst from SGR 1935+2154
  92. Fermi trigger No 652957973: Global MASTER-Net observations report
  93. Fermi trigger No 652944960: Global MASTER-Net observations report
  94. Fermi trigger No 652981861: Global MASTER-Net observations report
  95. GRB 210826A: further Swift-XRT observations
  96. GRB 210909B: GECAM detection
  97. GECAM observations of a series of bursts from SGR J1935+2154
  98. Swift detection of a burst from SGR Swift J1555.2-5402
  99. Fermi trigger No 652934203: Global MASTER-Net observations report
  100. GECAM observation of a burst from SGR J1935+2154

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